1. Field of the Invention
The present invention relates to a device which dehumidifies a gas stream and has a relatively high water adsorption capacity. The device can be incorporated into a garment or enclosure and is adapted to cool the user of a garment by evaporative cooling and provide microclimate control to an enclosure.
2. Background of the Invention
Garments designed to cool users while they are wearing the garment are known in the art. Typically, cooling devices and/or materials are incorporated into a portion of the garment to achieve such cooling. For example, U.S. Pat. No. 6,298,907 by Colvin et al. discloses a vest incorporating micropouches which contain a phase-change material (“PCM”) to cool a person wearing the vest. The micropouches are in thermal communication with the person wearing the vest and the PCM is selected such that as the body temperature of the person increases, the phase-change materials will change from a solid to a liquid phase at a selected temperature, thereby extracting heat from the individual at the selected phase-change temperature. Colvin et al. also discloses the use of air convection to cool the micropouches and further increase the efficiency of the vest.
However, phase-change materials have a relatively low cooling density for direct cooling of a person and typically have a phase change temperature significantly below body temperature (−37° C.). Moreover, PCMs are not effective where there is a possibility of vapor build up within the garment. For example, firemen, military and other public service personnel frequently use hazardous materials (Hazmat) suits when fighting fires and/or when undergoing biological and chemical warfare or corresponding training. Similar suits are also often used in an uncomfortably hot atmosphere, such as steel mills and deep mines and, as a result, the individual will often perspire significantly. The resulting perspiration can cause a rapid buildup of water vapor within the suit which lowers the user's rate of heat rejection. In the case of a sealed suit, the build-up of water vapor can cause visibility problems from condensation of the vapor on the user's visor. Physical and physiological discomfort may also result from the increased temperature of the suit and the build-up of perspiration on the user's skin and clothing.
U.S. Pat. No. 6,125,645 by Horn discloses the use of ice as a phase-change material within a garment to cool the individual. Aside from the impracticality of maintaining temperatures suitable to maintain the ice within the garment, ice has a low cooling density and has logistical disadvantages in that the ice must be available to the user at or near the hostile environment. Ice also cannot remove water vapor from the garment. In fact, as the ice melts, it will likely contribute to the humidification of the garment. The use of ice also suffers in that the user cannot control the rate of cooling within the garment.
In contrast to ice and phase-change materials, adsorption cooling can overcome many of these problems resulting in lighter or longer lasting cooling, simplified logistics, sustained visibility and controllability. The use of an adsorption cooler to cool air within a garment is disclosed in U.S. Pat. No. 6,601,404 by Roderick. Cooling loads from about 50W to about 500W for garment cooling applications and cooling temperatures of from about 10° C. to about 25° C. are disclosed.
U.S. Pat. No. 5,289,695 by Parrish et al. discloses a garment incorporating a desiccant. The desiccant adsorbs water generated during the wearing of the garment (e.g., perspiration) and is located adjacent to the outer surface of the garment or in a separate case. An open-cell thermal insulating layer is located opposite the exterior of the garment and adjacent to the desiccant to prevent heat from dissipating back toward the skin of the person wearing the garment. A phase-change material can be located between the users skin and the desiccant bed to enable thermal control within the garment by controlling the heat transfer to the adsorbent vest.
There remains a need for a lightweight water adsorption device for cooling an individual wearing a garment and/or controlling the micro-climate in an enclosure. It would be advantageous if the device could provide a high degree of water adsorption, thereby providing cooling and dehumidification, and did not require direct physical contact with the individual to accomplish the adsorption.